Field
An embodiment of the present invention relates to semiconductor memory devices.
Description of the Related Art
Variable-resistance memories (resistance RAMs [ReRAMs]) are one type of semiconductor memory devices that replace low-cost and large-capacity flash memories known in the art. A variable-resistance memory has memory cells each formed with a variable resistance film, and configures a cross-point memory cell array, allowing for the same level of capacity as flash memories. To further expand the capacity, some developed ReRAMs employ a so-called vertical bit line (VBL) structure, in which selection lines, or bit lines, are arrayed vertically with respect to the semiconductor substrate.